Esterification of cellulose materials



. BRETT W'YLAH AND-JOHN THOMAS, Oli GRANGEMOUTE,

OF. GBANGEMOUTH, STIRLING, SCOTLAND acetates is to treat the I6 Drawing. Application filed January :0,

Patented Feb. 25, 1930 UNITED. STATES PATENT, OFFICE.-

SCOTTISH DYES, LIMITED,

SCOTLAND, ASSIGNORS TO ESTERIFICATIOIN Oil? CELLULOSE 'MATERIALS This invention relates to the esterification of cellulose bodies, and more particularly to the production of cellulose acetate or acetates.

The usual method of obtaining cellulose cellulosic material in the presence of sulsulphuryl chloride or the like, which may, forgexample, act as a catalyst. It is usually the practice to carry out the reaction in the presence of an excess of acetic acid, serving, diluent and solvent.

The object of the present invention is to provide an improved or modified process for producing-cellulose acetate or acetates, these being either known or new bodies.

The invention connsists in a process for'the acetylation of cellulostic material by the action of an acetylating agent, which comprises the presence of pyridine sulphuric anhydride being synonymous with N-pyridinium or N-pyridinium sulphonic acid and is a combination of pyridine and sulphur trioxide, description of which may e found in Deutsche Ghemische Gesells'chaft Berichte 59 (1926) 1166.

The invention also consists in processes for the acetylation of cellulosic material substantially as herein described and which may be eiiected by heating with acetic anhydride or acetyl chloride in the presence of pyridine sulphuric anhydride.

The invention further consists in products which may be made according to processes substantially as herein described, or by the with acetic anhydride phuric acid, chlorine,

' eqluivalents of these processes, including a lulose acetate which contains up to about 56% of acetyl group.

The following examples illustrate how the invention may be carried into efiect, all parts referred to bemg parts by weight.

I Ewample I This deals with the roduction of a cellulose acetate only slight y soluble in acetone, but readily soluble in chloroform. 15 arts of pyridine sulphuric anhydride aread ed to G. On solution of the pyridine sulphuric anhydride, 15 parts of cellulose in the form for example, as a parts of acetic anhydride,' warmed to 100 1929, Serial No. 336,321, and in Great Britain January 26, 1928.

pyridine.

Ewaxmple II According to this example, cellulose acetate soluble in acetone is produced. 15 parts of pyridine sulphuric anhydride, 20 parts of glaclal acetic acid, and 10 parts of acetic anhydride are mixed, heated to 100 C., and 15 parts of paper cellulose added. The mix.- ture kept at 100 minutes, cooled, and poured'into water as in Example I. The product is soluble in acetone, in which it yields viscous solutions.

Example III lates and passes into solution glving a clear colourless viscous solution.

Example IV According to this example to a mixture of parts glacial acetic acid and 35 parts of acetyl chloride is added 1 part of pyridine sulphuro-anhydride .and heated to 60 C. until the latter has entirely dissolved. 16

C. is stirred ,for fifteen parts of paper cellulose are then added and the temperature "maintained at 6070 C.

for a periodgof 2 hours. Acetylation of the cellulose takes place and the paper di sol giving a clear colourless solutiom Example V According to this example to a mixture of 60 parts glacial acetic acid and 35 parts .of acetic anhydride is added 1 part of pyridine sulphuro-anhydride, and the temperature raised to 80 C. until the'latter completely dissolves. 16 parts of paper are then added and the mixture maintained at 80 C. for hour when a further 5 parts of acetic anhydride containing 0.5 part of pyridine-sulphuro-anhydride are put in and the melt maintained at 80 C. for onehour. Acetylation gradually takes place and the paper dissolves forming a clear colourless viscid solution of cellulose ester.

Example VII According to this example 60 parts of glacial acetic acid are mixed with 50 parts of acetic anhydride and 1 part of pyridine sulphuro-anhydride and the whole raised to 80 C. and stirred until the pyridine sulphuro-anhydride is in solution. 15 parts of paper pulp are then added, the temperature raised to 95 C. and kept at this for one hour. A further 10 parts of acetic anhydride and 1 part of pyridine sulphuro-anhydride are then added at 95 C. and the temperature maintained at this for 2 hours longer. The product obtained is a clear slightly yellow viscid solution.

General By the presence of pyridine sulphur trioxide, acetylation of cellulosic material may be readily carried into efl'ect. When this substance is used to assist the acetylation, the conditions may be varied so as to produce a number of difierent products which are soluble in different solvents, and which contain different amounts of combined acetic acid.

Some of the products, particularly the lower and middle members, are soluble in the ordinary solvents such as acetone and chloroform yielding viscous solutions which can be spun into threads or made into films or the like.

As regards the diluents, we find that acetic acid and its'derivatives, such as chloracetic ester and also chlorbenzene, chlortoluene and other chlorinated aromatic hydrocarbons are suitable.

Other cellulose materials may be used, such as for example, cotton wool and paper pulp.

The process may be so carried out as to yield, amongst other products, a cellulose acetate which contains up to about 56% of acetyl group. n

Having now described our invention, what We claim as new and desire to secure by Letters Patent is A process for the acetylation of cellulosic matter effected by heating with acetic anhydride in the presence of pyridine sulphuric anhydride.

In testimony whereof we have signed our names to this specification.

BIRKETT WYLAM. J. THOMAS. 

